A physically-based formulation for texture evolution during dynamic recrystallization. A case study of ice

Dynamic recrystallization can have a strong impact on texture development during the deformation of polycrystalline materials at high temperature, in particular for those with strong viscoplastic anisotropy such as ice. Owing to this anisotropy, recrystallization is essential for ensuring strain compatibility. The development of recrystallization textures leads to significant mechanical softening, both in laboratory or natural conditions (glaciers, ice sheets). Accurately predicting ice texture evolution due to recrystallization during tertiary creep remains a challenge, yet is crucial to account adequately for texture-induced anisotropy in large-scale models of glacial ice flow. We propose a new formulation for texture evolution due to dynamic recrystallization. This formulation is physically-based on an orientation attractor which maximizes the Resolved Shear Stress (RSS) on the easiest slip system in the crystal (basal slip for ice). The attractor is implemented in an equation of evolution of the crystal orientation with deformation, which is coupled to an anisotropic viscoplastic law (Continuous Transverse Isotropic - CTI) that provides the mechanical response of the ice crystal. The set of equations, which is the core of the R3iCe open source model is solved using finite elements method with a semi implicit scheme coded using the Rheolef library. R3iCe is validated by comparison with laboratory creep data for ice polycrystals under simple shear, uniaxial compression and tension. It correctly reproduces the texture evolution and the mechanical softening observed during tertiary creep. R3iCe therefore allows predicting enhancement factors that may be implemented in large-scale flow models. Although the validation was performed for ice, the R3iCe implementation is generic and applies for any material adequately described using a CTI law.

Ice is a polycrystalline material whose microstructure can induce strong viscoplastic anisotropy. Ice fabric (i.e preferred crystal orientations) and ice flow are closely linked: strong anisotropy of a polycristal develops as a result of its deformation history. Strong fabrics have indeed been observed both in nature and in laboratory experiments. In a glacier flow, such anisotropy can modify the directional viscosity of ice, making it locally harder or softer. Preferred crystal orientations may therefore influence glacier flow at large scale.To better characterize this influence, several models have been developed to predict fabric evolution coupled with glacier flow. However, the impact of fabric under near-melting temperature remains poorly quantified. In such conditions, dynamic recrystallization (DRX) is expected to strongly affect fabric evolution. Moreover, field observations that could constrain and validate fabric-evolution models in warm and highly dynamic flow are still scarce, leaving the role of ice textures in glacier dynamics unconstrained. As a result most large-scale glacier simulations still rely on isotropic rheologies combined with enhancement factors, which cannot adequately represent local anisotropy induced by evolving fabrics.R3iCe [1] is a full-field model using a finite element method that couples both the mechanical behavior and the texture evolution of polycrystalline ice. It was recently developed to predict the evolution of crystal orientations under constant strain rate or deviatoric stress, driven by viscoplastic deformation and dynamic recrystallization. R3iCe has been validated against different laboratory creep experiments, where it successfully reproduces both texture evolution and the associated mechanical softening during tertiary creep. However, the model remains untested under more complex deformation cases, such as those experienced by ice particles within real glacier flows.In this contribution, we extend the validated R3iCe model toward glacier-scale applications by constructing a R3iCe Flow Line (RFL) approach. It extracts the deformation history of Lagrangian ice parcels from large-scale glacier flow simulations, such as Elmer/ice, and provides the kinematic inputs required to drive R3iCe along glacier flow lines. The scheme is first validated using torsion experiments, which allow us to quantify the errors involved in predicting fabric evolution along a flow line in this controlled setting.R3iCe Flow Line is then applied to Argentière Glacier (French Alps), which is a temperate glacier. Near-surface samples collected in the ablation area are assumed to represent end-of-flow line fabrics, and are compared with RFL predictions driven by a transient Elmer/Ice flow simulation.By combining R3iCe Flow Line, a state-of-the-art Elmer/Ice simulation of Argentière Glacier flow, and field observations, this work aims to demonstrate the importance of accounting for fabric and its evolution under temperate, highly deforming conditions, where DRX is at play.[1] T.Chauve; M. Montagnat; V. Dansereau; P. Saramito; K. Fourteau; A. Tommasi. Comptes Rendus. Mécanique, Volume 352 (2024), pp. 99-134. doi: 10.5802/crmeca.243

Deformation characteristics of nanocrystalline TWIP steel under uniaxial tension and compression

Experiment and crystal plasticity analysis on plastic deformation of AZ31B Mg alloy sheet under intermediate temperatures: How deformation mechanisms evolve

Uniaxial ratcheting behaviours associated with microstructural development of unpeened and laser shock peened ASTM A 588 Grade D High Strength Low Alloy (HSLA) steel were studied in this investigation. The mechanism of plastic deformation and crystallographic texture evolution during ratcheting was also studied. For this, the primary experimental works involved were stress-controlled ratcheting fatigue tests (on unpeened/laser-peened specimens) at room temperature. Followed by this, microstructure and texture evolution on the surfaces and/or cross sections of the deformed specimens, using electron back scattered diffraction (EBSD) were studied in detail. Additionally, the substructural evolution of some selected samples was also studied using transmission electron microscopy (TEM). The results indicated that the average grain size of all the unpeened ratcheted specimens was marginally reduced after fatigue tests. The laser-peened specimen, however, showed a marginal increase in average grain size after ratcheting. Continuous dynamic recovery and recrystallisation (CDRR) during ratcheting was thought to be the cause of the observed reduction in average grain size in unpeened specimens, whereas continuous dynamic recrystallisation (CDRX) was believed to be the controlling factor for marginal accretion of grain size in laser-peened specimens. The plastic deformation of investigated steel was qualitatively explained by the observed dislocation patterns and their evolution.

Dynamic recovery and recrystallization mechanisms during ultrasonic spot welding of Al-Cu-Mg alloy

Mechanical response of single-crystal ${\mathrm{CsPbI}}_{3}, {\mathrm{CsPbBr}}_{3}, {\mathrm{CsPbIBr}}_{2}$, and ${\mathrm{CsPbI}}_{2}\mathrm{Br}$ is investigated under uniaxial tension and compression using molecular dynamics (MD) simulations. Stress-strain curves for these metal-halide perovskites are determined and mechanisms that strengthen and weaken them under plastic deformation are revealed. Our study finds the mechanical response of these crystals to differ considerably under uniaxial tension and compression. While ${\mathrm{CsPbI}}_{3}$ and ${\mathrm{CsPbBr}}_{3}$ exhibit a smooth elastic to plastic transition under uniaxial tension, distinct elastic and plastic regimes are observed under uniaxial compression. Only ${\mathrm{CsPbI}}_{3}$ is noted to exhibit strain hardening under uniaxial compression, which is deciphered to arise from generation of defects in the plastic regime. These defects, which take the form of deformation-induced distortion of the Pb-I octahedra, are shown to manifest as superlattice reflections in optical diffraction patterns derived from fast Fourier transform analysis of MD simulations. While a perfectly plastic postyield response is observed in ${\mathrm{CsPbIBr}}_{2}$ and ${\mathrm{CsPbI}}_{2}\mathrm{Br}$ under tension, a monotonic reduction in stress occurs after yielding under compression. Formation and growth of bands of high von Mises shear strain is revealed as an important plastic deformation mechanism in ${\mathrm{CsPbIBr}}_{2}$ and ${\mathrm{CsPbI}}_{2}\mathrm{Br}$ under uniaxial tension and compression. The evolution of defect microstructure with strain discussed here is expected to provide insights into plausible mechanisms that operate in metal-halide perovskites under experiments such as nanoindentation, while the defect-induced strengthening demonstrated here points to the possibility of fabricating robust perovskite films by engineering defects into the material.

In the current study, a rate-dependent crystal plasticity finite element method (CPFEM) was used to simulate flow stress behavior and texture evolution of a body-centered cubic (BCC) crystalline material during plastic deformation at room temperature. To account for crystallographic slip and rotation, a rate-dependent crystal constitutive law with a hardening model was incorporated into an in-house finite element program, CAMPform3D. Microstructural heterogeneity and anisotropy were handled by assigning a crystallographic orientation to each integration point of the element and determining the stiffness matrix of the individual crystal. Uniaxial tensile tests of single crystals with different crystallographic orientations were simulated to determine the material parameters in the hardening model. The texture evolution during four different deformation modes - uniaxial tension, uniaxial compression, channel die compression, and simple shear deformation - was investigated based on the comparison with experimental data available in the literature.

Crystallographic texture evolution in bulk deformation processing of FCC metals

TiB, TiC and La2O3 hybrid-reinforced Ti-6Al-4V matrix composites were fabricated by common casting and processed by the following forging and isothermal extrusion. The texture evolution, dynamic recrystallization (DRX) behavior and mechanical properties of the as-extruded composites were investigated. The results show that DRXed regions and deformed regions formed during extrusion, strong 〈0001〉α, $$ \left\langle {10\bar{1}0} \right\rangle_{\alpha } $$ and weak $$ \left\langle { 1 0 {\bar{\text{1}}\text{1}}} \right\rangle_{\alpha } $$ fiber textures parallel to extrusion direction were formed due to the selection of slip system in α phase and inheritance from phase transformation according to Burgers orientation relationship. Additionally, the orientation of α grain in DRXed regions became randomized in comparison with the deformed regions. Micro-sized TiB short fibers not only acted as source to generated dislocations, but hindered dislocation slip to cause pile-ups around TiB, which is beneficial to stimulate dynamic recrystallization. Submicro-sized La2O3 particles distributed at the triple junction of grain boundaries could pin grain boundaries and hinder grain growth. Tensile test results show that the ultimate tensile strength got a 9.8 pct enhancement, from 834.3 ± 10 to 916.0 ± 10.6 MPa, accompanied by simultaneous improvement of elongation from 5.4 ± 0.6 to 12.2 ± 0.7 pct at room temperature. The simultaneous increase of strength and ductility was principally attributed to TiB fracture modes and grain refinement after extrusion.

An austenitic Ni-30%Fe model alloy was employed to investigate the texture and substructure development within the deformed matrix and dynamically recrystallized (DRX) grains during hot torsion deformation. Both the deformed matrix and DRX grains predominantly displayed the crystallographic texture components expected for simple shear deformation. The characteristics of the deformed matrix texture evolution during deformation largely resulted from the preferred consumption of high Taylor factor components by new recrystallized grains. Likewise, the comparatively weaker crystallographic texture of DRX grains became increasingly dominated by low Taylor factor components as a result of their easier nucleation and lower consumption rate during DRX. There was a significant difference in the substructure formation mechanism between the deformed matrix and DRX grains for a given texture component. The deformed matrix substructure was largely characterized by “organized”, banded subgrain arrangements with alternating misorientations, while the substructure of DRX grains was more “random” in character and displayed complex, more equiaxed subgrain/cell arrangements characterized by a local accumulation of misorientations. Substructure characteristics of individual orientation components were principally consistent with the corresponding Taylor factor values.

Abstract. The recovery of a 1.5 million yr long ice core from Antarctica represents a keystone of our understanding of Quaternary climate, the progression of glaciation over this time period and the role of greenhouse gas cycles in this progression. Here we tackle the question of where such ice may still be found in the Antarctic ice sheet. We can show that such old ice is most likely to exist in the plateau area of the East Antarctic ice sheet (EAIS) without stratigraphic disturbance and should be able to be recovered after careful pre-site selection studies. Based on a simple ice and heat flow model and glaciological observations, we conclude that positions in the vicinity of major domes and saddle position on the East Antarctic Plateau will most likely have such old ice in store and represent the best study areas for dedicated reconnaissance studies in the near future. In contrast to previous ice core drill site selections, however, we strongly suggest significantly reduced ice thickness to avoid bottom melting. For example for the geothermal heat flux and accumulation conditions at Dome C, an ice thickness lower than but close to about 2500 m would be required to find 1.5 Myr old ice (i.e., more than 700 m less than at the current EPICA Dome C drill site). Within this constraint, the resolution of an Oldest-Ice record and the distance of such old ice to the bedrock should be maximized to avoid ice flow disturbances, for example, by finding locations with minimum geothermal heat flux. As the geothermal heat flux is largely unknown for the EAIS, this parameter has to be carefully determined beforehand. In addition, detailed bedrock topography and ice flow history has to be reconstructed for candidates of an Oldest-Ice ice coring site. Finally, we argue strongly for rapid access drilling before any full, deep ice coring activity commences to bring datable samples to the surface and to allow an age check of the oldest ice.

Effect of extension [formula omitted] twins on texture evolution at elevated temperature deformation accompanied by dynamic recrystallization

Microstructure and texture evolution during high-temperature compression of Al-Mg-Si-Zr-Mn alloy

Revealing the deformation behavior and microstructure evolution in Mg-12Y–1Al alloy during hot compression